The present invention relates to a clutch mechanism of a push-button tuner which may be used in a radio or the like for a vehicle, and more particularly, to a clutch mechanism suitable for push-button tuners having a low profile.
A known clutch mechanism for a push-button tuner is shown in FIGS. 1 and 2 by way of example.
Referring to the figures, numeral 1 designates a frame by which a manual tuning shaft 2 is turnably carried. The manual tuning shaft 2 is mounted perpendicularly to the plane of the frame 1, and its end protruding rightward from the frame 1 as viewed in FIG. 2 is formed with a pinion 2a.
On the other hand, numeral 3 designates a control lever, which is connected to a tuning slider, not shown, of the tuner. The tuning slider is operated by depressing a push button (not shown), and functions to move a core within a tuning coil. The control lever 3 is disposed in parallel with the plane of the frame 1, and has a rod portion 3a extended therefrom.
A clutch mechanism to be described below is disposed between the control lever 3 and the manual tuning shaft 2.
A pulley 4 having a V-shaped peripheral groove 4a adapted to receive the rod portion 3a is turnably carried by the frame 1 through a shaft 4b. A gear 5 is fixedly mounted on the shaft 4b, and meshes with the pinion 2a. A roller 6a for holding the rod portion 3a in pressed contact with the peripheral groove 4a is disposed below the rod portion 3a. The roller 6a is installed on one end of a bell crank lever 6, which is turnably carried on the frame 1 through a turning shaft 6b.
The other end of the bell crank lever 6 is turnably mounted on a clutch-release rod 7 through a pin 6c. The clutch-release rod 7 is operated by depressing a push button of the tuner so that a coiled spring 8 disposed between an end part of the clutch release rod 7 and the frame 1 turn the bell crank lever 6 in the clockwise direction as viewed in FIG. 1. In the normal state when the push button is not depressed, the rod portion 3a is held in pressed contact with the peripheral groove 4a by the roller 6a, and the clutch mechanism is in its engaged state (hereinbelow, the clutch mechanism is considered in its engaged state. When a push button of the tuner is depressed, the roller 6a is turned away from rod portion 3a to disengage the rod portion 3a from the peripheral groove 4a of the pulley 4.
When, the clutch mechanism is engaged, the manual tuning shaft 2 can be operated to turn the pulley 4 and reciprocate the control lever 3 to manually select a channel of the tuner. On the other hand, when a push button of the tuner is depressed, the clutch release rod 7 is moved leftward in FIG. 1 to disengage the pulley 4 from the rod portion 3a, and a channel selection by depressing the push button can be executed.
In such prior-art clutch mechanisms however, the manual tuning shaft 2 and the control lever 3 are mounted in directions orthogonal to each other, and the transmission and reduction means formed by the pinion 2 and the gear 5, as well as the motion conversion means formed by the pulley 4 having the peripheral groove 4a, the rod 3a, the roller 6a etc. and serving to convert a rotational motion into a rectilinear motion; are arranged between the manual tuning shaft 2 and the control lever 3. Therefore, the prior art has the problem that, due to the development of a conversion loss, a deviation is liable to occur between the operated tuning amount of the manual turning shaft and the moving amount of the core, so accurate manual tuning is difficult. Another problem is that the number of components is large.